In a printing method and apparatus of this sort as in a conventional system of rotary printing, e.g., as shown in JP 2005-335145 A, a web of paper for rotary press being printed on by an ink jet printer is fed to travel at an established speed in one direction from a paper feed unit to a paper takeup unit.
In the printing method and apparatus of this sort, it has hitherto been the case that for a variety of reasons such as of ending of printing data, printing data being divided for each of a number of the small number of prints, machine adjustments, checking of a printing state and operational convenience, there may en route be temporary halts or suspensions of printing from a continuous printing operation, the printing operation being subsequently reinitiated.
In the process in which a web of paper in the course of printing is fed to travel at a fixed speed as mentioned above, the web of paper, when the printing is suspended, still travels over a certain distance, leaving a blank portion due to inertia of the printing apparatus. And, when printing is reinitiated, the printing operation is initiated on a portion of paper following the blank portion of paper which has traveled over that distance after printing is temporarily suspended en route, with the result that such blank portions become mixed as NG portions of printed paper in a paper takeup roll downstream in the printing system.
Consequently, in the conventional digital printing method and apparatus of this sort the problem has come up that if a printing operation after it is temporarily suspended en route is reinitiated, in a tail end process of a printed paper takeup roll, the steps of processing NG portions of printed paper become complicated and troublesome. Moreover, noting that a printing speed exceeding 200 m/min is available in the latest printing process, the problem has arisen that a blank portion of printed paper produced when printing is suspended temporarily en route becomes elongated, thereby giving rise to an increase in the amount of broke or waste of paper.
Further, the conventional printing method and apparatus mentioned above has also entailed a problem that an increased force is caused to act on the web of paper both at a time it is brought to a temporary halt and at a time it is driven to initiate traveling.
In view of the foregoing problems, it is an object of the present invention to provide a digital printing method as well as an apparatus therefor which, if a consecutive printing operation after it is suspended temporarily en route is reinitiated, is capable of printing without producing waste of paper due to a portion left blank on a web of paper for rotary press and which is capable of so printing without causing an increased force to act on the web of paper both at a time it is brought to a temporary halt and at a time it is driven to initiate traveling.